Characterization of flexible Poly(vinyl butyral)/wood flour composites

Abstract The purpose of this study is to deeply characterize a flexible poly(vinyl butyral) (PVB)/wood flour (WF) recycled composite produced by an efficient and simplified processing strategy. The mixing of the PVB/WF composite (25, 40 and 55 wt%) was performed in a single screw extruder equipped with a Maillefer screw with mixer block type pineapple in the metering zone, with the screw operating in starved feed condition in its feeding zone. Thermogravimetric analysis showed that the thermostability of PVB is the limiting factor for the composite processing window and that prior drying of wood flour and PVB is important to avoid hydrolytic degradation. Although SEM analysis has shown the presence of WF aggregates when a high content of reinforcement is added, the extrusion process disperses the wood flour relatively well. The composites have a good interphase adhesion even without a coupling agent. Relative and true density linearly increased with wood flour incorporation, as predicted by the simple rule of mixture. The hardness of pure PVB is 18 Shore D and the composite with 55% WF has 60 Shore D hardness, an increase of 230%. The incorporation of the WF reduced the PVB damping effect but did not change significantly the glass transition temperature, kept around 30 °C. This study is very positive when the objective is the production of a flexible and natural composite from recycled materials in a simple and economically attractive way.